GRASSES OF IOWA. 203 



less than one-eighth of an inch-in length and width. They occur 

 on both surfaces of the leaf, but are more abundant on the 

 upper. These black spots are composed of a dense mycelium, 

 which in the green leaves bears numerous small spores which 

 serve to propagate the fungus in the summer. In dead leaves 

 small perithecia are found, which contain numerous elongated 

 bodies, the asci within which are found eight small, colorless 

 spores, known as ascospores; these latter carry the fungus 

 over the winter. In Iowa the grasses most commonly aifected 

 by this fungus are quack grass {Agropyron repens), wild rye 

 {Elymus robustus), Asprella hystrix, and Panicum Scribnerianum. 

 Occasionally this fungus is quite destructive. Frank,* Tubeuf, f 

 Treleasel and Pammel have given accounts of this fungus. 



BROWN SPOT OF WHEAT HEADS. 



The Phoma hennebrgii, Kuehn on wheat was first detected by 

 Kuehn.§ Frank |I has noted it in Germany and Eriksson*! for 

 Sweden. This fungus causes brown spots on the sterile and 

 flowering glumes In thes3 spots small perithecia occur. These 

 contain small, one-celled conidia. The kernels become spotted 

 and shriveled. Whole fields may be affected. Related to this 

 is the Phoma lopliistomoides, Sacc, which is a saprophyte, 

 according to Cavara.** The perithecia are small, 60-80" in diam- 

 eter, with an oblong ostiolum, and are immersed in the tissue. 

 The spores are small and thread-like, rounded at the ends, 

 8-10" long, .5-. 75" wide. 



BROWN SPOT DISEASE OF GRASSES. 



The Septoria graminum, Desm has received the name of 

 "Take-all" in Australia on account of the nature of its destruc- 

 tive work. N. A. Cobb says: "Taking the occurrence in spots, 

 as a starting point, I determined to see whether some other 

 characteristic symptom could not be made out, and in this I was 

 partially rewarded, for I found in the great majority of cases 

 that the plants dried up when young, mysteriously as some 

 farmers said, and left the ground bare or covered with weeds. 

 This will seem old news to farmers and hardly worth as much 



*Krankhelten der Pflanzen. 2: 455. /. 80. (Ed. 2.) 



♦Pflanzenkrankhelten. 243, 



tin Beal. Grass of N. Am. 1 : 424. 



^Fungus Diseases of Iowa Forage Plants. 24. 



§Rabenhorst Fung, Europ. 2261. 



llZelt, f. Pflanzenk. 3: 28. 



UMitth. d, K. Akad. Stockholm. 1890. 



•*Deber eine parasltlsche Pilze. Zsit, f- Pflanzenk. 3: 23. 



